Alejandro Lleras

University of Illinois, Urbana-Champaign | UIUC · Department of Psychology

People often look for objects in their immediate environment, a behaviour known as visual search. Most of the visual signals used during search come from peripheral vision, outside the direct focus of the eyes. In this Review, we present evidence that peripheral vision is both more capable and more complex than commonly believed. We then use three...

The linear separability effect refers to a benefit in search performance observed in a feature-search task, where target and distractor features vary along a continuous feature dimension: Search performance is best when there is a boundary in feature space that separates the distractor features from the target feature. However, the role that distra...

Visual working memory (VWM) content disrupts visual search performance when there is a singleton in the search array that is similar to the content in VWM, even when this singleton is task irrelevant. Typically, the memory-similar singleton captures attention, which results in slower search performance for memory-similar conditions compared to cond...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Objects differ from one another along a multitude of visual features. The more distinct an object is from other objects in its surroundings, the easier it is to find it. However, it is still unknown how this distinctiveness advantage emerges in human vision. Here, we studied how visual distinctiveness signals along two feature dimensions—shape and...

A common assumption in attention theories is that attention prioritizes search items based on their similarity to the target. Here, we tested this assumption and found it wanting. Observers searched through displays containing candidates (distractors that cannot be confidently differentiated from the target by peripheral vision) and lures (distract...

Emotional well-being depends on the ability to successfully engage a variety of coping strategies to regulate affective responses. Most studies have investigated the effectiveness of emotion regulation (ER) strategies that are deployed relatively later in the timing of processing that leads to full emotional experiences (i.e. reappraisal and suppre...

During production of the article, Figure 4 was incorrectly used twice in the initial article, so it appeared both as Figure 4 and Figure 5 in the article.

Feature Integration Theory (FIT) set out the groundwork for much of the work in visual cognition since its publication. One of the most important legacies of this theory has been the emphasis on feature-specific processing. Nowadays, visual features are thought of as a sort of currency of visual attention (e.g., features can be attended, processing...

In his seminal works, Endel Tulving argued that functionally distinct memory systems give rise to subjective experiences of remembering and knowing (i.e., recollection-vs. familiarity-based memory, respectively). Evidence shows that emotion specifically enhances recollection, and this effect is subserved by a synergistic mechanism involving the amy...

Objects in a scene can be distinct from one another along a multitude of visual attributes, such as color and shape, and the more distinct an object is from its surroundings, the easier it is to find it. However, exactly how this distinctiveness advantage arises in vision is not well understood. Here we studied whether and how visual distinctivenes...

When the spatial configuration of a search display is presented repeatedly, response times to finding the target within that configuration are shorter compared to completely novel configurations, even though observers do not have explicit recognition of the repetition. This phenomenon is known as Contextual Cueing and selective attention is thought...

Recently, Wang, Buetti and Lleras (2017) developed an equation to predict search performance in heterogeneous visual search scenes (i.e., multiple types of non-target objects simultaneously present) based on parameters observed when participants perform search in homogeneous scenes (i.e., when all non-target objects are identical to one another). T...

Stage 1 processing in visual search (e.g., efficient search) has long been thought to be unaffected by factors such as set size or lure-distractor similarity (or at least to be only minimally affected). Recent research from Buetti, Cronin, Madison, Wang, and Lleras (Journal of Experimental Psychology: General, 145, 672-707, 2016) showed that in eff...

Our lab recently found evidence that efficient visual search (with a fixed target) is characterized by logarithmic Reaction Time (RT) × Set Size functions whose steepness is modulated by the similarity between target and distractors. To determine whether this pattern of results was based on low-level visual factors uncontrolled by previous experime...

Recent results from our laboratory showed that, in fixed-target parallel search tasks, reaction times increase in a logarithmic fashion with set size, and the slope of this logarithmic function is modulated by lure-target similarity. These results were interpreted as being consistent with a processing architecture where early vision (stage one) pro...

Perceptual Load theory states that the degree of perceptual load on a display determines the amount of leftover attentional resources that the system can use to process distracting information. An important corollary of this theory is that the amount of perceptual load determines the vulnerability of the attention system to being captured by comple...

Previous work in our lab has demonstrated that efficient visual search with a fixed target has a reaction time by set size function that is best characterized by logarithmic curves. Further, the steepness of these logarithmic curves is determined by the similarity between target and distractor items (Buetti et al., 2016). A theoretical account of t...

Extant theories of the attentional blink propose that the most critical factor in determining second target accuracy is the time that elapses between the first and second targets. We report that this conclusion has overlooked an equally important determinant, namely, the frequency of the entraining stream in which these targets are embedded. Specif...

Priming of pop-out (PoP) refers to the facilitation of performance that occurs when a target-defining feature is repeated across consecutive trials in a pop-out oddball search task. The underlying mechanism of PoP has been poorly understood and raises important questions about how our visual system is guided by past experiences, even during bottom-...

We highlight the importance of considering the variance produced during the parallel processing stage in vision and present a case for why it is useful to consider the “item” as a meaningful unit of study when investigating early visual processing in visual search tasks.

A common assumption in several visual search theories is that the similarity between items in the display and the target template should impact or even determine the order in which those items are scrutinized during visual search. Here, we tested that assumption and failed to find support for it. We selected two different types of "candidate" stimu...

It has been shown that when humans require a brief moment of concentration or mental effort, they tend to avert their gaze away from the attended location (or even blink). Similarly, participants tend to miss unexpected events when they are highly focused on a task. We present an Engagement Theory of Distractibility that is meant to capture the rel...

Most current models of visual processing propose that there are 2 main stages of visual processing, the first consisting of a parallel visual analysis of the scene and the second being a precise scrutiny of a few elements in the scene. Here, we present novel evidence that the first stage of processing adds systematic variance to visual processing t...

Recently, our lab demonstrated a logarithmic relationship between reaction time and the number of items in a search display (e.g., Lleras & Buetti, VSS 2014; Cronin, Buetti, and Lleras, VSS 2014). Until now, the Reaction Time X Set-Size function was thought to be linear. Lleras and colleagues' displays differed from typical search displays in that...

Feature singleton search tasks have been characterized as being independent of the number of non-target elements in the display (Treisman and Gelade, 1980; Wolfe, 1994). Previous work from our lab has shown that reaction times on feature singleton search tasks in fact increase logarithmically with the number of non-target (lure) elements in the dis...

Several traditional accounts of visual search propose that search is completed in two separate sequential stages: a preattentive stage and a capacity-limited attentive stage. We challenge such accounts by showing that the first stage is an attentive stage of unlimited capacity. This stage gathers evidence in parallel at each location across the vis...

Intertrial effects such as priming of pop-out (PoP) often occur for task-irrelevant dimensions as well as task-relevant dimensions, though to a weaker extent. Here we test the hypothesis that increased priming for task-relevant dimensions is due to greater passive build-up of priming for the task-relevant dimension rather than to an active filterin...

Past theories of visual search for a feature singleton in a display dictate that visual search is highly efficient and RTs are basically unrelated to the number of elements in the display (Treisman & Gelade, 1980). Here, we show evidence that this view is fundamentally wrong. Lleras, Cronin and Buetti (submitted) proposed a new theory of visual sea...

During visual search, it is typically thought that possible targets (candidates) are selected from a search set, then serially inspected until the target is found (e.g., Wolfe, 1994). The relationship between search set-size and the amount of time it takes to locate the target is traditionally thought to be linear: the more items present, the longe...

Traditional models of visual search propose (a)that visual search is driven by similarity such that attentional priority is given to those objects most similar to the target and (b)that attentional efficiency is indexed by the slope of the search function. Here we show evidence that both of these basic tenants of visual search are fundamentally wro...

Masked priming effects are taken as evidence that behavior can be influenced by information that does not reach our phenomenal awareness and hence serves as a dissociation between perception and awareness. Priming with unseen stimuli in studies using metacontrast masking procedure are well established, while priming in object-substitution masking (...

In a typical pop-out task, there is one target and a varying number of distractor stimuli. Now imagine a target-absent display in the context of a pop-out task: all items are identical, and it is decidedly easy to conclude that all items in the display are distractors, precisely because there is no target to select on that display. One may be tempt...

The ventral attentional network (VAN) is thought to drive "stimulus driven attention" [e.g., Asplund, C. L., Todd, J. J., Snyder, A. P., & Marois, R. A central role for the lateral prefrontal cortex in goal-directed and stimulus-driven attention. Nature Neuroscience, 13, 507-512, 2010; Shulman, G. L., McAvoy, M. P., Cowan, M. C., Astafiev, S. V., T...

Recent studies of rapid resumption-an observer's ability to quickly resume a visual search after an interruption-suggest that predictions underlie visual perception. Previous studies showed that when the search display changes unpredictably after the interruption, rapid resumption disappears. This conclusion is at odds with our everyday experience,...

While attentional effects in visual selection tasks have traditionally been assigned "top-down" or "bottom-up" origins, more recently it has been proposed that there are three major factors affecting visual selection: (1) physical salience, (2) current goals and (3) selection history. Here, we look further into selection history by investigating Pr...

It is often the case that stimuli (or aspects of a stimulus) are referred to as being "task-irrelevant." Here, we recount where this label originated and argue that the use of this label is at odds with the concept of "relevance" that has arisen in the contingent-capture literature. This is not merely a matter of labels, but a matter of inference:...

We discuss how, at the present time, there is a large deal of confusion in the attention literature regarding the use of the label “distractor” and what may be inferred from experiments using distractors. In particular, investigators seem to use the concepts of distractor interference and distractibility almost interchangeably. In contrast, we argu...

ABSTRACT Young and older adults searched for a unique face in a set of three schematic faces and identified a secondary feature of the target. The faces could be negative, positive, or neutral. Young adults were slower and less accurate in searching for a negative face among neutral faces when they had previewed a display of negative faces than whe...

http://nobaproject.com/chapters/vision

It is well known that observers can implicitly learn the spatial context of complex visual searches, such that future searches through repeated contexts are completed faster than those through novel contexts, even though observers remain at chance at discriminating repeated from new contexts. This contextual-cueing effect arises quickly (within les...

We used a time perception task to study the effects of the subjective experience of control on emotion and cognitive processing. This task is uniquely sensitive to the emotionality of the stimuli: high-arousing negative stimuli are perceived as lasting longer than high-arousing positive events, while the opposite pattern is observed for low-arousin...

Humans perceive time with millisecond precision. However, when experiencing negative or fearful events, time appears to slow down and aversive events are judged to last longer than neutral or positive events of equal duration. Feelings of control have been shown to attenuate increases in arousal triggered by anxiety-provoking events. Here, we teste...

Rhythmic events are common in our sensory world. Temporal regularities could be used to predict the timing of upcoming events, thus facilitating their processing. Indeed, cognitive theories have long posited the existence of internal oscillators whose timing can be entrained to ongoing periodic stimuli in the environment as a mechanism of temporal...

People can selectively maintain task-relevant features of items in visual working memory (Woodman & Vogel, 2008), but can they effectively ignore task-irrelevant features of an attended item? And, if so, does the ability to ignore irrelevant feature dimensions correlate with visual short-term memory (VSTM) capacity? Participants performed a priming...

Visual search for emotional faces is influenced by the valence of the faces and/or observers’ prior search experience. Here, we asked young and older adults to search for a face showing a unique emotion (emotion oddball) and to identify a second feature of the target. We investigated how previewing a display of homogeneous emotional faces affected...

Background / Purpose: We analyzed eye movements of participants while they were occupied doing a primary mental task of varying cognitive difficulty. Completely task irrelevant images appeared on the display as new onsets, while nothing else occurred in the display. We computed the degree of attentional capture by the onset of these images. Main...

What are the behavioral consequences of moving attention to a location only to find a no-go stimulus there (i.e., a stimulus that does not afford a response in the task)? To test this question, we used displays containing three go stimuli and a no-go stimulus. Participants were asked to report the identity of the target pointed at by a central cue...

When searching for an oddball target, the stimulus in the preceding trial influences performance on the current trial. Responding to a target among two distractors on the current trial is faster when the preceding trial had the same target and distractors colors than when the target and distractor colors were switched (priming of Pop-out, PoP). Fin...

Young and older adults indentified the shape of a color oddball in a visual search task, and both showed faster and more accurate responses when the distractor color was passively viewed in the preceding target-absent trial than when the target color was previewed. This inter-trial effect, known as the distractor previewing effect (DPE), reflects a...

Alpha oscillations are ubiquitous in the brain, but their role in cortical processing remains a matter of debate. Recently, evidence has begun to accumulate in support of a role for alpha oscillations in attention selection and control. Here we first review evidence that 8-12 Hz oscillations in the brain have a general inhibitory role in cognitive...

We newly propose that the vigilance decrement occurs because the cognitive control system fails to maintain active the goal of the vigilance task over prolonged periods of time (goal habituation). Further, we hypothesized that momentarily deactivating this goal (via a switch in tasks) would prevent the activation level of the vigilance goal from ev...

Previous studies have shown that even in the context of fairly easy selection tasks, as is the case in a pop-out task, selection of the pop-out stimulus can be sped up (in terms of eye movements) when the target-defining feature repeats across trials. Here, we show that selection of a pop-out target can actually be delayed (in terms of saccadic lat...

A recent study by Lou (1999) looked at Troxler fading and concluded that it is driven by attentional selection, as well as by display properties such as eccentricity. The present study sought to extend Lou's findings. Two specific questions were addressed. First, how does the fading depend on the structure of the attended objects? Second, is the du...